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  <h1 class="topictitle1">priority_queue_node Template Class</h1>
 
   
  <div> 
	 <div class="section"><h2 class="sectiontitle">Summary</h2> 
		 
		<p>An unbounded buffer of messages of type 
		  <span class="keyword">T</span>. Messages are forwarded in priority order. 
		</p>
 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Syntax</h2> 
		 
		<pre>template&lt; typename T,
          typename Compare = std::less&lt;T&gt;,
          typename A = cache_aligned_allocator&lt;T&gt; &gt;
class priority_queue_node;</pre> 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Header</h2> 
		 
		<pre>#include "tbb/flow_graph.h"</pre> 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Description</h2> 
		 
		<p>A 
		  <span class="keyword">priority_queue_node</span> is a 
		  <span class="keyword">graph_node</span>, 
		  <span class="keyword">receiver&lt;T&gt;</span> and 
		  <span class="keyword">sender&lt;T&gt;</span> that forwards messages in priority
		  order to a single successor in its successor set. Successors are tried in the
		  order that they were registered with the node. If a successor rejects the
		  message, it is removed from the successor list as described by the policy in
		  the Message Passing Protocol, and the next successor in the set is tried. This
		  continues until a successor accepts the message, or all successors have been
		  attempted. Items that are successfully transferred to a successor are removed
		  from the buffer. 
		</p>
 
		<p>The next message to be forwarded has the largest priority as
		  determined by 
		  <span class="keyword">Compare</span>. 
		</p>
 
		<p>A 
		  <span class="keyword">priority_queue_node</span> is reservable and supports a
		  single reservation at a time. While the 
		  <span class="keyword">priority_queue_node</span> is reserved, no other items will
		  be forwarded to successors and all 
		  <span class="keyword">try_get</span> calls will return 
		  <span class="keyword">false</span>. While reserved, 
		  <span class="keyword">try_put</span> will still return 
		  <span class="keyword">true</span> and add items to the 
		  <span class="keyword">priority_queue_node</span>. 
		</p>
 
		<p>An allocator of type 
		  <span class="keyword">A</span> is used to allocate internal memory for the 
		  <span class="keyword">priority_queue_node.</span> 
		</p>
 
		<p><span class="keyword">T</span> must be copy-constructible and assignable. 
		</p>
 
		<p>Rejection of messages by successors is handled using the protocol in
		  the Message Passing Protocol, see link below. 
		</p>
 
		<div class="Note"><h3 class="NoteTipHead">
					Caution</h3> 
		  <p> The <samp class="codeph">Compare</samp> function object must not throw an exception.
		  </p>
 
                </div>
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Members</h2> 
		 
		<pre>namespace tbb {
namespace flow {
 
template&lt; typename T, typename Compare = std::less&lt;T&gt;,
          typename A = cache_aligned_allocator&lt;T&gt;&gt;
class priority_queue_node : public queue_node&lt;T&gt; {
public:
    typedef size_t size_type;
    priority_queue_node( graph &amp;g );
    priority_queue_node( const priority_queue_node &amp;src );
    ~priority_queue_node();
 
    // receiver&lt;T&gt;
    typedef T input_type;
    typedef sender&lt;input_type&gt; predecessor_type;
    bool try_put( const input_type &amp;v );
    bool register_predecessor( predecessor_type &amp;p );
    bool remove_predecessor( predecessor_type &amp;p );
 
    // sender&lt;T&gt;
    typedef T output_type;
    typedef receiver&lt;output_type&gt; successor_type;
    bool register_successor( successor_type &amp;r );
    bool remove_successor( successor_type &amp;r );
    bool try_get( output_type &amp;v );
    bool try_reserve( output_type &amp;v );
    bool try_release( );
    bool try_consume( );
};
 
}
}</pre> 
		
<div class="tablenoborder"><table cellpadding="4" summary="" frame="border" border="1" cellspacing="0" rules="all"><span class="tabledesc">The following table provides additional information on the
			 members of this template class. 
		  </span><thead align="left"> 
				<tr> 
				  <th class="cellrowborder" valign="top" width="33.89830508474576%" id="d80049e148">Member 
				  </th>
 
				  <th class="cellrowborder" valign="top" width="66.10169491525423%" id="d80049e151">Description 
				  </th>
 
				</tr>
</thead>
 
			 <tbody> 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">priority_queue_node( graph &amp;g
						)</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Constructs an empty 
						<span class="keyword">priority_queue_node</span> that belongs to the 
						<span class="keyword">graph g</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">priority_queue_node( const
						priority_queue_node &amp;src )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Constructs an empty 
						<span class="keyword">priority_queue_node</span> that belongs to the
						same 
						<span class="keyword">graph g</span> as 
						<span class="keyword">src</span>. The list of predecessors, the list of
						successors and the messages in the buffer are NOT copied. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool try_put( const input_type
						&amp;v )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Adds 
						<span class="keyword">v</span> to the 
						<span class="keyword">priority_queue_node</span>. If 
						<span class="keyword">v</span>'s priority is the largest of all of the
						currently buffered messages, a task is spawned to forward the item to a
						successor. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool register_predecessor(
						predecessor_type &amp;p )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Never rejects puts and therefore does not need to maintain a
						list of predecessors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool remove_predecessor(
						predecessor_type &amp;p )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Never rejects puts and therefore does not need to maintain a
						list of predecessors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool register_successor(
						successor_type &amp;r )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Adds 
						<span class="keyword">r</span> to the set of successors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool remove_successor(
						successor_type &amp;r )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Removes 
						<span class="keyword">r</span> from the set of successors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool try_get( output_type &amp;v
						)</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if a message is available in the node
						and the node is not currently reserved. Otherwise returns 
						<span class="keyword">false</span>. If the node returns 
						<span class="keyword">true</span>, the message with the largest
						priority will have been copied to 
						<span class="keyword">v</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool try_reserve( output_type
						&amp;v )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>If the call returns 
						<span class="keyword">true</span>, the node is reserved and will
						forward no more messages until the reservation has been released or consumed. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if a message is available in the node
						and the node is not currently reserved. Otherwise returns 
						<span class="keyword">false</span>. If the node returns 
						<span class="keyword">true</span>, the message with the largest
						priority will have been copied to 
						<span class="keyword">v</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool try_release( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Releases the reservation on the node. The item that was
						returned in the last successful call to 
						<span class="keyword">try_reserve</span> remains in the 
						<span class="keyword">priority_queue_node</span>. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if the buffer is currently reserved
						and 
						<span class="keyword">false</span> otherwise. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d80049e148 "><span class="keyword">bool try_consume( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d80049e151 "> 
					 <p>Releases the reservation on the node. The item that was
						returned in the last successful call to 
						<span class="keyword">try_reserve</span> is popped from the front of
						the queue. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if the buffer is currently reserved
						and 
						<span class="keyword">false</span> otherwise. 
					 </p>
 
				  </td>
 
				</tr>
 
			 </tbody>
 
		  </table>
</div>
 
	 </div>
 
  </div>
 
  
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong>&nbsp;<a href="../../reference/flow_graph.htm">Flow Graph</a></div>
</div>
<div class="See Also">
<h2>See Also</h2>
<div class="linklist">
<div><a href="message_passing_protocol.htm">Message Passing Protocol 
		  </a></div></div>
</div>

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